Co-occurring mental health (MH) and substance use disorders (SUD) are common among virally unsuppressed people with HIV (PWH), and improving the health outcomes of ?hard-to-reach? populations will require new approaches to integrating treatment for HIV, MH and SUD. The Max Clinic in Seattle, Washington is a novel ?low-barrier? clinic that has successfully increased viral suppression among PWH with complex medical and social needs. Expansion of low-barrier care is central to Seattle/King County?s Ending the HIV Epidemic plan, and similar clinics are being implemented in other U.S. cities, but inadequate MH and SUD treatment is a critical deficit of the model that must be addressed. The overall goal of this two-year R34 proposal is to develop a replicable strategy of implementing collaborative care management (CoCM) for the treatment of depression and opioid use disorder (OUD) in a Ryan White-funded low-barrier HIV clinic. CoCM is supported by robust evidence for improving the treatment of depression in primary care and for managing OUD treatment with a nurse care manager. To our knowledge, CoCM has not yet been studied in patient populations with complex comorbidities and social needs, and the impact of CoCM for mental health and/or SUD conditions on viral suppression has not been studied among PWH in the U.S. Our approach is guided by the EPIS framework (exploration, planning, implementation, sustainment). For Aim 1, we will develop a CoCM model to integrate depression and OUD treatment into a low-barrier HIV care setting for patients who have not had continuous viral suppression in the past year. We will use a compilation of strategies to implement the model (including planning, restructuring, and education strategies), and stakeholder input will guide iterative refinement of the model. For Aim 2, we will evaluate the feasibility, acceptability, and appropriateness of the adapted CoCM model in a low-barrier clinic and assess changes in behavioral health outcomes among patients enrolled in CoCM after 6 months. We will enroll 35 patients in CoCM as part of standard care during the grant period. To evaluate feasibility, acceptability, and appropriateness, we will conduct qualitative interviews with Max Clinic patients (N=15) and service delivery stakeholders (N=15) before and after implementation of CoCM. To assess whether CoCM retains its effectiveness in the setting of the Max Clinic, we will evaluate the impact of the intervention on depression and OUD outcomes among patients enrolled in CoCM at 6 months. To refine tools and processes for collecting data of interest for a future study, we will enroll 40 patients in a study to assess the following factors at baseline and 6-month follow-up: substance use other than opioids, anxiety symptoms, housing stability, jail incarceration, employment, health-related quality of life, and emergency room and hospital utilization. These studies will generate crucial preliminary data to design a future study in multiple settings.